Katherine Barlow was Green Lake's school teacher. She made the best spiced peaches in Texas. The children loved Miss Katherine, as did the men she taught. Barlow had a friendship with the black onion picker, Sam; they'd often exchange a jar of peaches for a bag of onions respectively. One day, when Sam went to go deliver some onions to her, he noticed the leaking roof of the schoolhouse. He told her he'd fix it for her in exchange for 3 jars of peaches. Every time he fixed one thing, he'd find another thing to fix for her. This made them develop a relationship together, and they discovered mutual affection. One day, she and Sam were discovered kissing each other. This was not allowed in the town at the time, due to the racism in the south. Sam was going to be hanged for this crime, so Barlow tried to reason with the drunk sheriff. He did nothing to appease the situation. Being afraid of his impending doom, Sam took off in his boat to avoid the hanging, but was instead shot in the middle of the lake. Barlow witnessed the entire thing, and was so mournful of his death, that she shot the sheriff and kissed him on the cheek (leaving behind a red lipstick mark).
Louis Sachar stated in an interview that Kate Barlow is his favorite character from Holes.
Barlow became a famous outlaw, killing multiple men and leaving a kiss on their cheek. She robbed numerous banks in Texas and several individuals including Stanley's ancestor, Stanley Yelnats I. But didn't kill him; she left him in the desert to die. She became incredibly rich with the fruits of her labor, and hid the money away somewhere.
Many years later, Barlow returns to the lake sitting against Sam's boat Mary Lou. Yellow-spotted lizards began to swarm around her, though not attacking. Trout and his wife, Linda (one of Barlow's former students), aim their guns at her and ask her where the treasure is. Kate replied, "Go ahead and kill me, Trout, but I sure hope you like to dig. 'Cause you're going to be digging for a long time. It's a big vast wasteland out there. You, and your children, and their children, can dig for the next hundred years and you'll never find it." She then grabs a yellow-spotted lizard, prompting it to bite her. Barlow dies laughing, telling them, "You'd better start diggin' Trout."